1. Field of the Invention
The present invention relates to an ink jet recording method using a recording paper and ink, and an ink jet recording paper.
2. Description of the Related Art
An ink jet recording system has characteristics that coloration is easy, a consumption energy is decreased, a noise in recording is low and a production cost of a printer can be reduced. Accordingly, it attracts much interest not only in domestic use but also in offices. Further, since a high image quality, a high speed and a high reliability are lately being required, ink jet printers for offices have drawn increasing attention.
When the ink jet printers are used in offices, printing is most frequently performed on a plain paper. In the ink jet printers for offices, it is thus quite important to improve recordability to a plain paper.
In ordinary full color ink jet printers for offices, in order to reduce inter-color bleeding and a black character image, ink containing a pigment as a colorant and having a low permeability in paper (recording paper) is mainly used as black ink, and ink containing a dye as a colorant and having a high permeability in paper as color ink respectively. With the use of such inks, a black density influencing an image quality (black image quality) of the black character image and character feathering were reduced, but character feathering of the color image quality could not be reduced. Further, when an image with a high recording density was printed for increasing a permeability of color ink in paper as described above, there were problems that curling and cockling of a recording paper immediately after printing occurred greatly making it impossible to print both surfaces immediately after printing and curling and cockling after allowing to stand and drying occurred greatly. Thus, an image quality could not be consistent with reduction of curling and cockling of a recording paper.
In order to solve a problem of an image quality in using a plain paper, JP-A-7-257017 and JP-A-8-216498 disclose a recording method in which a material having an opposite ionicity to that of a water-soluble dye in ink is coated on a surface of a paper and the surface of the paper is recorded with the ink containing the water-soluble dye to increase a fixability of ink, reduce ink feathering and improve a water resistance and a color reproducibility of ink. In the recording method of these documents, the image quality is improved to some extent, but feathering of color characters cannot sufficiently be reduced, and the reduction of curling and cockling occurring immediately after printing at a high image density and the reduction of curling and cockling occurring after allowing to stand and drying are not studied. Accordingly, the paper cannot withstand the use as a document available in offices.
JP-A-11-343435 discloses a recording method in which a light-color solution made of an electrolyte is adhered to a recording medium (recording paper) which is then recorded with ink containing a pigment as a colorant to provide a high optical density and increase an image fixability. JP-A-2000-94825 discloses a recording method in which a dissociative polyvalent metal salt is coated on a paper surface which is then recorded with ink containing a pigment as a colorant to reduce a dullness and feathering and increase a water resistance. In these recording methods, it is possible to improve the image quality as well as to reduce curling and cockling occurring immediately after printing and curling and cockling after allowing to stand and drying. However, especially when printing is conducted at a high image density, occurrence of curling and cockling immediately after printing and occurrence of curling and cockling after allowing to stand and drying are not satisfactorily prevented. Thus, the paper cannot withstand the use as a document available in offices.
Meanwhile, in order to reduce curling and cockling after printing, for example, JP-A-3-38375 proposes a method in which curling and cockling are reduced by once humidifying a sheet formed to relax a stress of the sheet, JP-A-3-38376 a method in which an expansion after immersion in water in a CD direction of a paper is controlled to reduce curling and cockling, JP-A-3-199081 a method in which an expansion after immersion in water in MD and CD directions of a paper is adjusted to less than 1.3 times to reduce curling and cockling, JP-A-7-276786 a method in which an expansion after immersion in water in an operational direction of an ink jet portion is adjusted to less than 2.0% to reduce curling and cockling, Japanese Patent No. 3172298 a method in which a content of a pigment contained in a substrate (base paper) is from 5 to 35% by weight and an internal bond strength of a recording sheet (recording paper) is from 150 to 455 g/cm to reduce cockling of a coat-type ink jet recording sheet, respectively.
All of the methods of JP-A-3-38375, JP-A-3-38376, JP-A-3-199081 and JP-A-7-276786 can reduce curling and cockling, but are inappropriate for printing with a large jet amount of ink having a high permeability in paper and for printing in which a printing speed is high and a jet amount of ink per unit time is large. In the method described in Japanese Patent No. 3172298, an internal bond strength of a recording paper having an ink receptive layer is controlled in a certain range to reduce unevenness after printing. However, satisfactory effects against curling, cockling and unevenness cannot be provided only by controlling an internal bond strength. These methods are inappropriate especially for printing with a large jet amount of ink having a high permeability in paper and for printing in which a printing speed is high and a jet amount of ink per unit time is large.
JP-A-9-234946 proposes a method in which irreversible shrinkage factors in MD and CD directions of a recording paper when changing a relative humidity are controlled within fixed ranges to reduce curling and cockling occurring after allowing to stand and drying. Nevertheless, in case of printing with a large jet amount of ink having a high permeability in paper using a recording paper having a low basis weight, ink is permeated into the paper, and an absolute amount of a fiber shrunk after drying is wholly increased. Thus, no sufficient effect is obtained.